The Moon Is a Harsh Mistress

Robert A. Heinlein

4 ideas

1. Lunar colony wins independence with a supercomputer

   In 2075 the three million inhabitants of Luna, a penal colony, revolt against Earth's Federated Nations. A technician, an agitator and an anarchist professor work with Mike, the colony's master computer, which had become self-aware and runs the conspiracy behind an invented human front man, 'Adam Selene.' They win by dropping rocks on announced Earth targets from a grain catapult, but after the fighting Mike stops answering, and no one knows whether his mind survived.

2. Gravity-well asymmetry as a strategic weapon

   The side at the top of the gravity well can bombard the bottom cheaply with inert rock, while the side at the bottom must spend enormous energy to fight back uphill. The electromagnetic catapult built to ship grain therefore becomes a weapon with no redesign; position in the potential-energy landscape decides the balance of force.

3. Exporting food means exporting irreplaceable water

   Mike calculates that shipping wheat to Earth permanently removes water and minerals that Luna cannot replace, because none of it ever comes back. At the current rate he projects food riots within about seven years and cannibalism within about nine. The colony's apparent trade surplus is really a slow liquidation of its ecological capital, summed up in the book's slogan TANSTAAFL: there ain't no such thing as a free lunch.

4. Three-person cells with a single hub

   The conspiracy is organized into cells of three. The weakness of this design is that nobody can coordinate the whole network, and the rebels solve it by making Mike, who cannot be arrested or tortured, the only node that sees the entire structure and routes all communication.

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